Flexible displays made with a technology known as electronic ink, or E ink, exhibit good brightness and contrast, a wide viewing angle and little or no power consumption are currently being exploited for applications in which a portable reusable display medium is necessary, such as in reusable paper. One way to make a reusable medium that is portable is to remove the driving electronic from the electronic display and use external addressing electrodes to write and erase images.
Generally, an encapsulated electrophoretic display includes one or more species of particles that either absorb or scatter light. One example is a system in which the capsules contain one or more species of electrophoretically mobile particles dispersed in a dyed suspending medium. Another example is a system in which the capsules contain two separate species of particles suspended in a clear suspending fluid, in which one of the species of particles absorbs light (black), while the other species of particles scatters light (white). Other extensions are possible, including more than two species of particles, with or without a dye, etc. The particles are commonly solid pigments, dyed particles, or pigment/polymer composites.
The gyricon, also called the twisting-ball display, rotary ball display, particle display, dipolar particle light valve, etc., offers a technology for making a form of electric paper. A gyricon is an addressable display made up of a multiplicity of optically anisotropic balls, each of which can be selectively rotated to present a desired face to an observer. Thus, in one version at least, the gyricon is a solid microsphere, hemispherically-colored black and white and having hemispherically-opposing zeta potentials. Each gyricon rotates within a dielectric oil-filled microcavity formed in the media upon exposure to an externally-applied electric field.
Unfortunately, currently available portable reusable displays suffer from problems with long term stability and can be destabilized by an electric field or even by static charge that builds up during normal handling. Therefore, in order to make portable reusable displays more reliable and convenient to use, it would be desirable to have a portable reusable display medium that is stable in the presence of an electric field and, in particular, is not destabilized by electrostatic discharge.